The present invention generally relates to a high performance oxygen separation material and methods for making the same and, more specifically, to a polymer bound nitrogen adsorbent system for the production of oxygen by adsorbing nitrogen from air.
Gas separation is important to support a variety of commercial, industrial and medical needs. An adsorbent is used in on-board oxygen generation system (OBOGS) applications to remove nitrogen from the air, thereby enriching oxygen concentration in the outlet stream. The nitrogen separated from the air stream is then removed from the system using a higher temperature (temperature-swing adsorption) or a lower pressure (pressure-swing adsorption).
In addition to the use of this type of system on high performance military airplanes, adsorbent-based OBOGS offers a very large improvement for commercial transport systems by replacing the current stored oxygen systems. Pressurized or chemically-bound oxygen storage systems require on-board consumables and therefore have very limited capacity. An adsorbent-based oxygen source enables longer high-altitude emergency operations, thereby extending emergency operational range.
In any aerospace application, component size and weight are crucial factors that determine the success of the technology. Therefore, any system that may be reduced in size or weight, especially in aerospace applications, is a significant achievement.
Referring FIG. 1, there is shown a conventional method 100 for producing an immobilized OBOGS adsorbent. Materials, such as zeolite 13X, which have preferential affinities for nitrogen relative to oxygen are used to remove nitrogen and thereby concentrate oxygen. Generally, these materials are produced as small crystallites 102, which are bound with clay to form 1 mm beads 104 as shown in the step indicated by arrow 106. The clay binder reduces the available zeolite capacity by dilution and may also further reduce gas access to the zeolite by fouling zeolite pores. The beads 104 may be immobilized with an organic binder and activated by conventional methods (such as thermal treatment) as shown at arrow 108 to form an immobilized OBOGS adsorbent 110. The organic binder currently in use has a tg (glassy temperature) in the range of 210° C. which is not high enough temperature for complete activation; at least 340° C. is required for complete water removal.
As can be seen, there is a need for a method for making an oxygen separation material that provides higher zeolite concentration by using less binder, thereby reducing the weight necessary to devote to the oxygen separation material. There is also a need to produce this material in a matrix that is stable to a temperature of at least 340° C.